Optical coherence tomography (OCT) has established itself as a non-contact method for retinal imaging. OCT has a higher axial resolution than other retinal imaging methods such as scanning laser ophthalmoscopy and fundus imaging. High sensitivity, axial resolution, and speed are important attributes for probing the retina at the cellular level. While the axial resolution (z-direction) using OCT can be up to 3 μm in retinal tissue, the lateral resolution (xy-direction) of retinal imaging systems is typically reported to be at best 15 μm due to the aperture of the eye, and presence of ocular aberrations. With the introduction of spectral-domain OCT (SD-OCT) for retinal imaging, retinal tomograms may be made at video rate, without loss of sensitivity or resolution.
Advances in OCT have allowed for the detection of polarization properties of layers within the retina. The devices which have capacity for polarization detection are referred to as polarization-sensitive optical coherence tomography (PS-OCT) devices. Additional detail on PS-OCT may be seen in United States Patent Application publication number 2007/0038040, which is incorporated herein by reference. Layers of the retina which are known to have distinct polarization properties include the birefringent nerve fiber layer and Henle's fiber layer, diattenuating photoreceptor layer, and depolarizing retinal pigment epithelium. Additionally, polarization changes are proposed to be a sensitive indicator of cellular health. Further, it is thought that diseases of the eye such as glaucoma and age-related macular degeneration may be diagnosed and assayed based on the polarization properties of retinal cells. The level of resolution possessed by PS-OCT currently though, is inadequate for visualizing the polarization properties of cell types associated with these diseases.
Adaptive Optics (AO) is a technology used to improve the performance of optical systems by reducing the effects of optical aberrations. This improved performance is generated by measuring the aberrations in a wavefront and compensating for them with a spatial phase modulator, sometimes called a wavefront corrector or deformable mirror.
Therefore, since current apparatuses cannot detect many important microscopic structures, such as individual retinal cells, it is desirable to have a PS-OCT system which is capable of resolution better than 15 μm. Production of such a system would facilitate the visualization of structures associated with the formation or presence of various retinal conditions, such as glaucoma and age-related macular degeneration.